Matsunaga, the president of a real estate company, spends his week in a secret hideaway to forget his title and social status. One day, he meets Fumiko at the hideaway, a girl who has a mysterious charm, and is gradually attracted to him. Matsunaga deepens his relationship with her, but suddenly a mysterious man appears.
Matsunaga's secret hideaway is a rundown house. One day, Fumiko, a young girl, enters his hideaway and introduces herself to him. They talk and get to know each other. The next time he is on his way to his hideaway, Matsunaga sees Fumiko standing by the side of the street, like how a prostitute would wait for potential clients to pass by. So I guess she could be a hooker. When she sees him, she runs to him and follows him to his hideaway. They hang out that night and have sex and so begins their affair (he is married).
A mysterious man appears and confronts Fumiko. He looks poor and maybe homeless. I'm not sure what his previous relationship was with Fumiko. Is he an ex-lover? An ex-client or maybe her pimp? Was he rich and successful before and his luck just changed? One thing's for sure, he's obsessed with Fumiko. She runs away from him but when he catches up to her, he offers her money which she accepts. We don't know what happens after that as it isn't shown.. does she fuck him for the money?
We see the mysterious man approach and talk to Matsunaga, and then in the next scene, he approaches Fumiko in a park and offers her money again, this time in the form of coins. She doesn't take the money outright but she comes with him, suggesting she may be servicing him again.
The mysterious man goes on to harass Matsunaga and Fumiko. Matsunaga calls him to his office, maybe to sort things out with him, but nothing is resolved in their meeting.
One night, Fumiko gives Matsunaga an emergency call, asking him to go to the park because the mysterious man is after her. We see her hiding beside a building while on the phone with Matsunaga, while we see the mysterious man looking around the park, searching for her.
Matsunaga comes to the park, but what he finds when he arrives is Fumiko having sex with the mysterious man in the public restroom! His knees weakened at the discovery and he slumps on the floor outside the restroom. He confronts her when she comes out of the restroom but it just ends up with her hugging him.
While Matsunaga and Fumiko hang out in the hideaway, the mysterious man comes and attacks them with a knife. The couple ends up killing him and burying his body in the dirt under the floor of the house, and then they have sex after.
Near the end part of the film, Matsunaga sees a young guy exiting his hideaway as he arrives and is about to go in. When he comes in, he sees his mistress wearing nothing but panties, and also sees some money on a desk, so he thinks that she's still whoring despite being with him. They have a confrontation, which could turn into tragedy.